package com.hit.basmath.learn.others;

/**
 * 221. Maximal Square
 * <p>
 * Given a 2D binary matrix filled with 0's and 1's, find the largest square containing only 1's and return its area.
 * <p>
 * Example:
 * <p>
 * Input:
 * <p>
 * 1 0 1 0 0
 * 1 0 1 1 1
 * 1 1 1 1 1
 * 1 0 0 1 0
 * <p>
 * Output: 4
 */
public class _221 {
    public int maximalSquare(char[][] a) {
        if (a.length == 0) return 0;
        int m = a.length, n = a[0].length, result = 0;
        int[][] b = new int[m + 1][n + 1];
        for (int i = 1; i <= m; i++) {
            for (int j = 1; j <= n; j++) {
                if (a[i - 1][j - 1] == '1') {
                    b[i][j] = Math.min(Math.min(b[i][j - 1], b[i - 1][j - 1]), b[i - 1][j]) + 1;
                    result = Math.max(b[i][j], result); // update result
                }
            }
        }
        return result * result;
    }
}
